Formation and use of pollen grains

Pollen is a mass of microspores produced by a seed plant that appears as fine dust when it is harvested. Each pollen grain is a minute body with a variety of shapes and structures that develops in the male structures of seed-bearing plants and is transferred to the female structures by a variety of mechanisms (wind, water, insects, etc.) where fertilization takes place. The anthers of the stamens in flowers create pollen in angiosperms, which are flowering plants. The micro strobili of gymnosperms are created by the growth of the microsporophylls (male pollen cones). Pollen is made up of one or more vegetative cells and one or more reproductive cells, depending on the species. A pollen grain is not the male gamete in and of itself. Plants called angiosperms and certain gymnosperms have vegetative cells that form the pollen tube that develops to meet the unfertilized ovules, and the reproductive cell produces the sperm. In angiosperms and certain gymnosperms, the reproductive cell is responsible for fertilization. The majority of pollen grains are composed of three different sections. The nuclei that are responsible for fertilization are found in the centre cytoplasmic region of the cell. The inline and the exile are two additional layers that make up the wall of the grain: an inner layer called the inline and an exterior one called the exile. A portion of the intine is composed of cellulose or hemicellulose, at the very least. The exine layer, which is the outermost and most lasting layer, is extremely resistant to disintegration; treatment with high temperatures, strong acids, or strong bases does not affect it. In the scientific community, sporopollenins are the compounds that make up the exine. Unlike the internal sections of the pollen grain, which are rapidly broken down, the exine layer, and thus the general structure of the pollen grain, is easily preserved in many kinds of sediments; the quality of preservation may vary depending on the environmental conditions in which it occurs.

Pollen grain in brief 

Pollen is a powdery material generated by flowering plants and other seedlings. It is composed of pollen grains (very reduced microgametophytes), which are responsible for the production of male gametes (sperm cells). Pollen grains are coated with a hard substance called sporopollenin, which protects gametophytes as they migrate from the stamens to the pistil of flowering plants or from the male cone to the female cone of gymnosperms, respectively. Whenever pollen comes into contact with a suitable pistil or female cone, it germinates, resulting in the formation of a pollen tube that transports sperm to the ovule, which contains the female gametophyte. Individual pollen grains are so minute that magnifying them is necessary to view the fine details. Palynology is the study of pollen, and it is extremely valuable in a variety of fields such as paleoecology, palaeontology, archaeology, and forensics. Plant pollen is utilized in cross-pollination to transmit haploid male genetic material from the anther of a single bloom to the stigma of another flower, a process known as pollination. This procedure occurs from the anther of one flower to the stigma of another flower when it occurs by self-pollination.

Formation of pollen grain

Pollen is produced in the microsporangia of a conifer or other gymnosperm’s male cone, or the anthers of an angiosperm’s flower, depending on the species. Pollen grains are found in a vast variety of forms, sizes, and surface patterns that are unique to each species they come from (see electron micrograph, right). Wings are present on the pollen grains of pines, firs, and spruces. The forget-me-not (Myosotis spp.) pollen grain measures 2.5-5 microns (0.005 millimetres) in diameter, making it the smallest pollen grain known. Corn pollen grains are big, measuring approximately 90–100 microns. The majority of grass pollen is between 20 and 25 microns in size.

During flower formation in angiosperms, the anther is made of a mass of cells that appear undifferentiated, except for a dermis that is partially differentiated. Anthers include four groups of sporogenous cells, which divide and multiply as the flower grows. The fertile sporogenous cells may be surrounded by layers of sterile cells that have grown into the pollen sac wall. In other cases, the cells mature and develop into nutritive cells, which provide sustenance for the microspores that arise as a result of meiotic division in the sporogenous cells.

Uses

Pollen is used to influencing the characteristics of plants. Cross-pollination is the process of fertilization between plants that are genetically similar to improve them. Cross-pollination has resulted in the development of plants that are resistant to pests and dehydration, as well as an increase in crop production, to name a few benefits. Archaeologists can also utilize pollen to identify what ancient civilizations ate for sustenance by analyzing the pollen.

Pollination is the process of pollen being transported from the stamen to the stigma of a flower. It is possible to pollinate a flower by yourself if pollen grains are transported from one another to another on the same flower, or from one flower to another on the same plant. Cross-pollination happens when pollen grains from one plant of the same species are deposited on the stigma of another plant of the same species. Pollen distribution in flowering plants and gymnosperms is dependent on the presence of exogenous agents or vectors. Wind, living organisms, and water are all examples of pollination vectors. In general, flower architecture and pollen grains are suited to the type of pollinating vector that is actively involved in pollination. When it comes to grasses, wind pollination is quite common. Grass pollen is light, dry, and abundant, and it is released in vast amounts. Pollen grains are frequently structurally changed to aid in their passage through the air. Pollination by living vectors is often more complex, including a long interaction between the plant and the vector, during which co-adaptations have evolved to facilitate pollination. Even though insects are by far the most numerous pollinators of plants, other live pollinators such as mammals and birds, as well as some reptiles, also play an important role.

Conclusion

The male gametophytes are represented by the pollen grains. Each pollen grain has a two-layered wall that protects it from the environment. High temperatures, as well as strong acids and alkalis, can be tolerated by the exine layer, which is composed of sporopollenin, which is one of the most resistant organic materials available, allowing them to withstand high temperatures and strong acids and alkalis. There is currently no enzyme known to digest sporopollenin. Exine’s germ pores are defined as the portion of the cell wall where sporopollenin is absent. It contributes to the development of the pollen tube. The thin inner layer is referred to as the intine layer. It is made up of two components: cellulose and pectin. A mature pollen grain has two cells: the vegetative cell and the generative cell. The vegetative cell is responsible for pollen production. The vegetative cell is larger, has a larger food reserve, and contains a nucleus that is irregularly formed in shape. The generative cell is tiny and floats in the cytoplasm of the vegetative cell, which is surrounded by a protective membrane. Pollen grains are discharged by angiosperms in this 2-celled stage in around 60 percent of cases. Preceding pollen grains being discharged in the remaining species, the generative cell divides mitotically to produce two male gametes from which to choose (3 celled stages).